Additional resources provided by the author
 United Nations Office on Drugs and Crime
 “National Results on Drug Use” September 2013 by Johnston LD et al. in Monitoring the Future.
 National Highway Traffic Safety Administration Office of Behavioral Safety Research
 Colorado Revised Statue 42-4-1301
 “Impact of Prolonged Cannabinoid Excretion in Chronic Daily Cannabis Smokers' Blood on Per Se Drugged Driving Laws” February 2013 by Robert S. Goodwin, et al. in the Journal of Clinical Chemistry
 “Phase I and II Cannabinoid Disposition in Blood and Plasma of Occasional and Frequent Smokers Following Controlled Smoked Cannabis” February 2014 by Nathalie A. Desrosiers et al. in the Journal of Clinical Chemistry
 “Scientists Still Seek A Reliable DUI Test For Marijuana” July 30, 2017 by Rae Ellen Bichell at NPR